1. Field of the Invention
The present invention relates to a method of manufacturing a pattern of conductive fine-line films on a substrate for an electronic circuit board, and a setting ink used for the same.
2. Description of the Prior Art
Conventionally, conductive fine-line film wirings with a width of 50 .mu.m or less were formed by photolithography employing etching. The photolithography is an excellent technology capable of forming fine-line patterns of scores of microns in width at high precision, but it requires many complicated process including photoresist coating, exposure, development, etching, and washing, and the apparatuses used in exposure, development, etching and others are large and expensive. In the conventional photolithography, accordingly, the manufacturing cost was very high. On the other hand, the screen printing is an inexpensive pattern forming technique. But, it is difficult for this technique to form conductive fine-line films of several scores of microns stably and at high precision.
In relation to these problems, U.S. Pat. No. 4,479,432 discloses a method of thick film printing using an intaglio and silicone rubber rollers. This method realizes printing of thick film fine-line wiring in a width of 30 .mu.m to 100 .mu.m, and a thickness of about 5 to several scores of microns. In this method, however, since a rubber of relatively soft hardness of 30 degrees or less (JIS K 6301 Shore hardness A) is used, the rubber is easily deformed, and it is impossible to print fine-line patterns excellent in dimensional precision. Besides, the intaglio is generally manufactured by the wet etching process. When a steel-made intaglio made by the wet etching process is used, it is difficult to form the groove edges in an extremely excellent linearity. Accordingly, in this method, if fine-line wiring of several scores of microns be printed, it is difficult to obtain a fine-line wiring of sufficiently excellent linearity, and it is impossible to print fine-line wiring in the order of 10 .mu.m at high quality. Yet, in the intaglio offset printing method, since the end of the fine-line wiring being printed tends to be round, it is impossible to form fine-line patterns with rectangular-shaped ends of fine-line wiring.